Redeye is the appearance of an unnatural reddish coloration in the pupils of a person appearing in an image captured by a camera with flash illumination. Peteye is the appearance of an unnatural coloration (not necessarily red) of the pupils in an animal appearing in an image captured by a camera with flash illumination. Redeye and peteye are caused by light from the flash illumination reflecting off the retina and returning to the camera. Redeye typically results from light reflecting off blood vessels in the retina, whereas peteye typically results from light reflecting off a reflective layer of the retina.
Image processing techniques have been proposed for detecting and correcting redeye in color images of humans. These techniques typically are semi-automatic or automatic. Semi-automatic redeye detection techniques rely on human input. For example, in some semi-automatic redeye reduction systems, a user must manually identify to the system the areas of an image containing redeye before the defects can be corrected. Many automatic human redeye reduction systems rely on a preliminary face detection step before redeye areas are detected. A common automatic approach involves detecting human faces in an image and, subsequently, detecting eyes within each detected face. After the eyes are located, redeye is identified based on shape, coloration, and brightness of image areas corresponding to the detected eye locations.
Detecting and correcting peteye are significantly more difficult than detecting and correcting redeye because peteye may be any of a variety of colors and face detection cannot be used to localize peteyes in an image. In addition, the reflective retinal layer that is present in the eyes of many animals, such as dogs and cats, can cause a variety of peteye colors as well as brightly glowing large white peteyes. Although techniques for detecting and correcting redeye in images may be used to correct some peteyes, such systems and methods cannot satisfactorily detect and correct the majority of peteyes that appear in images. What are needed are systems and methods that are designed specifically to detect and correct peteyes in images.